linux-kernel - [PATCH RESEND 2/4] dma: dma-axi-dmac: fix HW scatter-gather not looking at the queue

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Message-Id: <20251104-axi-dmac-fixes-and-improvs-v1-2-3e6fd9328f72@analog.com>
Date: Tue, 04 Nov 2025 16:22:26 +0000
From: Nuno Sá via B4 Relay <devnull+nuno.sa.analog.com@...nel.org>
To: Vinod Koul <vkoul@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
 Paul Cercueil <paul@...pouillou.net>
Cc: Michael Hennerich <Michael.Hennerich@...log.com>, 
 dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RESEND 2/4] dma: dma-axi-dmac: fix HW scatter-gather not
 looking at the queue

From: Nuno Sá <nuno.sa@...log.com>

For HW scatter gather transfers we still need to look for the queue. The
HW is capable of queueing 3 concurrent transfers and if we try more than
that we'll get the submit queue full and should return. Otherwise, if we
go ahead and program the new transfer, we end up discarding it.

Fixes: e97dc7435972 ("dmaengine: axi-dmac: Add support for scatter-gather transfers")
Signed-off-by: Nuno Sá <nuno.sa@...log.com>
---
 drivers/dma/dma-axi-dmac.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
index e22639822045..0f25f6d8ae71 100644
--- a/drivers/dma/dma-axi-dmac.c
+++ b/drivers/dma/dma-axi-dmac.c
@@ -233,11 +233,9 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
 	unsigned int flags = 0;
 	unsigned int val;
 
-	if (!chan->hw_sg) {
-		val = axi_dmac_read(dmac, AXI_DMAC_REG_START_TRANSFER);
-		if (val) /* Queue is full, wait for the next SOT IRQ */
-			return;
-	}
+	val = axi_dmac_read(dmac, AXI_DMAC_REG_START_TRANSFER);
+	if (val) /* Queue is full, wait for the next SOT IRQ */
+		return;
 
 	desc = chan->next_desc;
 

-- 
2.51.0